The present invention relates to the intravenous administration of nutrients and therapeutic agents to patients and, more particularly, to methods and apparatus for administering intravenous hyperalimentation.
Ingestion, digestion, and absorption of food and assimilation of resulting substrates into the body cell mass are vital functions of the gastrointestinal tract. These functions may be impaired in a variety of ways. For example, infants born with gastrointestinal abnormalities, adults who develop gastrointestinal diseases, burn or accident victims, cancer patients, etc., may be unable to maintain their nutritional and fluid balance by oral intake. Without proper treatment they may die from starvation and dehydration.
Traditional intravenous feeding, i.e., through relatively small veins in the limbs, has severe limitations. A patient with one of the above described maladies may initially require eight liters or more of intravenous fluid per day with enough fats, proteins, and carbohydrates to meet the body's nutritional requirements and maintain positive nitrogen balance. Beyond three liters per day, however, the excess fluid strains the cardiovascular system. A diuretic may be given so that the kidneys can process the additional fluid. However, this method is dangerous.
Another approach is to increase the concentration of nutrients in the intravenous solutions. However, such solutions cannot be dripped into a relatively small vein in the arm or leg without severe pain coupled with the risk of vein inflammation and/or thrombosis.
In the early 1960's Dr. Stanley J. Dudrick and his colleagues developed a method of intravenous nutritional support (referred to in the medical profession as a hyperalimentation or total parenteral nutrition) by which normal growth and development as well as a positive nitrogen balance could be maintained. An open ended catheter was threaded through a moderate sized vein such as the subclavian, accessible under the collarbone, and into a very large vein, the superior vena cava. Because of the very large flow of blood through the superior vena cava a concentrated solution delivered through the catheter is rapidly diluted, thus allowing administration of a high concentration of nutrients without risk of pain, venous inflammation, or thrombosis.
Since Dr. Dudrick's initial work extensive research and development has been done with intravenous nutritional solutions. It has been possible to supply up to 7000 calories per day intravenously. Different apparatus and methods have evolved for short and long term intravenous therapy. With the latter, the distal end of the catheter is routed subcutaneously to an exit point midway down the anterior wall of the chest. The patient can then couple the catheter to a source of nutrients in the home and thus avoid prolonged hospitalization while still obtaining intensive intravenous nutritional therapy.
Serious problems heretofore encountered with hyperalimentation include potentially fatal air embolism which may occur when the distal end of the catheter becomes disconnected; severe or fatal hemorrhage which may also occur if the end of the catheter becomes disconnected; and blood reflux into the open proximal end of the catheter which may result in blood clots which interfere with and stop the flow of intravenous solution through the catheter. These clots may also form the nidus for bacterial or fungal growth which may then give rise to serious or fatal septicemias. If blood clots from the catheter enter the circulatory system the consequences may be serious or fatal. Therefore, it has been necessary to flush out the catheter with an anticoagulant as often as every four hours.
In order to avoid metabolic disorders due to excesses or deficiencies in the administrations of intravenous nutritional therapy it is necessary to control the amounts of nutrients and fluids supplied. Heretofore, every known apparatus for intravenous hyperalimentation has utilized costly pumps and flow sensing devices for controlling the rate of fluid administration, both to prevent too rapid administration which would result in severe metabolic disorders, and to prevent flow stoppage which may result in clotting in the catheter, making it unusable. A photoelectric sensor or some other device must be used to shut off the pump when the solution bottle has emptied otherwise a serious and possibly fatal air embolus will occur. If the pump is non-operative for just a short period of time, blood will reflux into the open proximal end of the catheter, causing a blood clot which may render the catheter inoperative or lead to other previously described complications.
Other problems involve the amount of hardware which must remain coupled to the distal end of the catheter after insertion. This inhibits the patient's mobility and increases the risk of accidental dislodgement, kinking, or cutting of the catheter. Furthermore, if intravenous therapy is temporarily suspended, the catheter must be flushed with an anticoagulant solution as frequently as every four hours to prevent blood clots from forming in the catheter. Finally, methods of passing the catheter through the subcutaneous tissue for permanent placement have been cumbersome and require separate tunnelling and threading procedures.
Catheters with one way valves adjacent their closed proximal ends have been used to deliver cerebrospinal fluid to the atrium of the heart. However, catheters with proximal one way valves have not heretofore been utilized to accomplish intravenous administration of nutrients or therapeutic agents, including total parenteral nutrition.